Dynamic bearing manufacturing method

ABSTRACT

A method of manufacturing a dynamic bearing comprises providing a bearing having a through hole. A photoresist is coated on an inner wall of the through hole. An ultraviolet lamp capable of inserting into the through hole is provided. A mask having patterns of pressure-generating grooves is attached to the surface of the ultraviolet lamp. The ultraviolet lamp is inserted into the through hole to perform an exposure process with the mask. The exposed portions of photoresist are developed to appear portions of the inner wall underneath. The appeared portions of the inner wall are etched to form grooves on the bearing, and finally, the photoresist remaining on the inner wall of the through hole is stripped.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method of manufacturing a dynamic bearing, and in particular to a method of fabricating a dynamic bearing utilizing photolithography.

2. Description of the Related Art

A dynamic bearing comprises fine pressure-generating grooves on the inner walls thereof. As the axle of a motor spins, lubricant in the pressure-generating grooves is drawn to distribute between axle and the bearing and generate dynamical pressure therebetween, which reduces the friction between the axle and the bearing and eliminates the noise due to the friction. The pressure-generating grooves on the inner wall of the bearing, however, are difficult to be fabricated because of the minute scale of width and depth thereof. The costs of conventional manufacturing methods such as cutting, rolling, injection, or combination etc. are very high because these methods need special processing tools and skills. In addition, pressure-generating grooves processed by cutting processing often cause breach at the turning point and have inconsistent depth and width. Furthermore, the expensive processing machine and fragile cutting tools cannot be effectively and efficiently applied to mass production.

BRIEF SUMMARY OF THE INVENTION

The invention provides a method of manufacturing a dynamic bearing by photolithography to simplify the formation of pressure-generating grooves on the inners wall of bearing.

According to the invention, a method of manufacturing a dynamic bearing, comprises the steps of: providing a bearing having a through hole; applying a photoresist .on an inner wall of the through hole of the bearing; providing an ultraviolet lamp capable of entering into the through hole; attaching a mask having patterns of pressure-generating grooves to the surface of the ultraviolet lamp; inserting the ultraviolet lamp into the through hole to expose the photoresist through the mask; removing the exposed portions of photoresist to make its underneath portions of the inner wall appear; etching the appeared portions of the inner wall to form grooves; and stripping the remaining photoresist from the inner wall of the bearing.

Preferably, the bearing is made of copper or metal and is baked after the photoresist is applied on its inner wall.

The patterns of pressure-generating grooves of the mask are transparent and the other portion of the mask is opaque.

The mask can further comprise a pattern of an oil reservoir thereon for forming an oil reservoir on the inner wall of the bearing.

The method of the present invention can reduce costs as result of automated or semi-automated mass production, and form the identical and uniform grooves in any kinds of shapes in the inner wall of a bearing with ease.

A detailed description is given in the following with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 is a cross section of a bearing according to an embodiment of the invention;

FIG. 2 is a cross section of a bearing coated with photoresist on the inner wall thereof according to an embodiment of the invention;

FIG. 3 shows a lamp used in an exposure process according to an embodiment of the invention;

FIG. 4 is a diagram of an exposure process according to an embodiment of the invention;

FIG. 5 is a diagram of a bearing after developing process according to an embodiment of the invention; and

FIG. 6 is a diagram of a bearing after etching and stripping process according to an embodiment of the invention.

DETAILED DESCRIPTION OF INVENTION

According to the invention, a method of manufacturing dynamic bearing at first is to form a desired shape of a bearing having a through hole by cutting or turning or by powder sintering way. The bearing is preferably made of copper.

An inner wall 10 defining the through hole is coated with a photoresist 20 uniformly, as shown in FIG. 2, by spray coating, dipping, spin coating or centrifugal coating. The photoresist 20 coated on the inner wall 10 comprises polyimide, diazonium salt, or sulfonamide chlorine. In this embodiment of the invention, the photoresist 20 coated on the inner wall 10 is a kind of positive photoresist, for example “Electrolube PRP-200.”

Then, the photoresist 20 coated on the inner wall 10 is dried by baking process for securing the adhesion between the inner wall 10 and the photoresist 20. As shown in FIG. 3, an ultraviolet lamp 30 with a mask 40 attached on the surface thereof is provided. The mask 40 comprises patterns of pressure-generating grooves 401 and an oil reservoir 402 thereon. The ultraviolet lamp 30 is preferably a cold cathode fluorescent lamp or an optical fiber illuminant, which can emit ultraviolet light having wavelength ranging from 350 nm to 450 nm. With positive photoresist in this embodiment, the patterns of pressure-generating grooves 401 and oil reservoir 402 are transparent on the mask and the other portion thereof is opaque. In this embodiment, the groove on the mask is V-shaped. As shown in FIG. 4, after baking process, the ultraviolet lamp 30 with the mask 40 attached thereon is inserted into the through hole of the bearing, and activated to emit ultraviolet light to execute an exposure process. During the exposure process, a part of the photoresist 20 is sensitized by the ultraviolet light emitted from the ultraviolet lamp 30 through the patterns on the mask 40.

After the exposure process, as shown in FIG. 5, the ultraviolet lamp 30, is removed, and the exposed photoresist is removed by a developer to make the underneath portions of the inner wall 10 appear. The concentration of the developer is determined by the type of photoresist. In this embodiment, NaOH solution is used to serve as a developer.

After the developing process, the bearing is cleaned by water, and then the appeared portions of the inner wall are etched to form grooves 12 and an oil reservoir 13. The etchant can comprise ferric chloride, cupric chloride or ammonium sulfide solution.

After the etching process, the bearing is cleaned by water, and the photoresist remaining on the inner wall is stripped by a stripping solution such as alcohol, and then is cleaned by water. The finished dynamic bearing of the invention is shown in FIG. 6.

The feature of the invention is to form the pressure-generating grooves on the inner wall of a bearing by photolithography, so the solutions used in this invention are not limited. In addition, the grooves on the inner wall are also not limited in any shape, and it can be in fish bone shape, substantially-modified-X-shape, twill or straight stripe shape.

Finally, while the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements. 

1. A method of manufacturing a dynamic bearing, comprising the steps of: providing a bearing having a through hole; coating a photoresist on an inner wall of the through hole of the bearing; inserting an ultraviolet lamp having at least one pattern of groove into the through hole and performing an exposure process; removing the photoresist to expose portions of the inner wall by a developer; and etching the exposed portions of the inner wall to form at least one groove by an etchant.
 2. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the pattern of groove is formed on a mask attached to the surface of the ultraviolet lamp.
 3. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the mask further comprises a pattern of oil reservoir.
 4. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the shape of the pattern of groove comprises V-shape, substantially-modified-X-shape, fish bone shape, twill or straight stripe shape.
 5. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the bearing is baked after the inner wall is coated with the photoresist.
 6. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the bearing and the through hole thereof are formed by cutting, turning or powder sintering.
 7. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the photoresist is coated on the inner wall by spray coating, dipping, spin coating or centrifugal coating.
 8. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the ultraviolet lamp comprises a cold cathode fluorescent lamp or optical fiber illuminant.
 9. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the inner wall of the bearing is cleaned by water after the developing step.
 10. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the inner wall of the bearing is cleaned by water after the etching step.
 11. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein a stripping solution is used to remove the residual photoresist on the inner wall after the etching step.
 12. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the bearing comprises copper or metal.
 13. The method of manufacturing a dynamic bearing as claimed in claim 1, wherein the photoresist is a positive photoresist.
 14. The method of manufacturing a dynamic bearing as claimed in claim 13, wherein the photoresist comprises polyimide, diazonium salt, or sulfonamide chlorine.
 15. The method of manufacturing a dynamic bearing as claimed in claim 13, wherein the pattern of groove is transparent, while the other portion of the mask is opaque.
 16. The method of manufacturing a dynamic bearing as claimed in claim 15, wherein the ultraviolet lamp emits ultraviolet light having the wavelength ranging from 350 nm to 450 nm.
 17. The method of manufacturing a dynamic bearing as claimed in claim 16, wherein the developer comprises sodium hydroxide solution.
 18. The method of manufacturing a dynamic bearing as claimed in claim 17, wherein the etchant comprises ferric chloride, cupric chloride or ammonium sulfide solution.
 19. The method of manufacturing a dynamic bearing as claimed in claim 18, wherein after the etching step, the residual photoresist on the inner wall is removed by alcohol.
 20. A method of manufacturing a dynamic bearing, comprising the steps of: providing a bearing having a through hole, and an ultraviolet lamp; applying a photoresist on an inner wall of the through hole of the bearing; attaching a mask having patterns of at least one pressure-generating groove and an oil reservoir on the surface of the ultraviolet lamp; inserting the ultraviolet lamp into the through hole to perform an exposure process; removing the photoresist to expose portions of the inner wall; etching the exposed portions of the inner wall to form grooves and oil reservoir thereon; and stripping the photoresist remaining on the inner wall. 